In order to produce white light for small screen LCD backlighting, it is now common to position red LED dice, green LED dice and blue LED dice together in one package. Various configurations of red, green and blue LED dice which attempt to address problems concerning light mixing and thermal management. There are well known problems with producing a well-mixed white light from a combination of red, green and blue LED dice within a constrained space. There is the problem of heat sinking and heat dissipation for light sources in the LCD display. There is also the problem of mixing multiple-colored light sources to provide a uniform color and a uniform luminance for the LCD backlighting. Furthermore, there are the issues with respect to minimizing the hot spot area and increasing the active area on the LCD.
Referring to FIGS. 12A, 12B, 13A and 13B, there is shown a side emitting LED package 5. In FIGS. 12A and 12B, there is shown a light guide plate 10 coupled to side emitting LED package 5. There are several disadvantages of this typical backlighting configuration. Generally, color mixing is not optimum due to the wide pitch between adjacent LED packages 5 so as to cause dark spots 15, which in turn cause hot spots and reduce the active area for the LCD.
Side emitting LED die 20, which is also referred to as LED chip 20, is positioned within package 5 and electrically and thermally connected to the surrounding environment by an electrical and heat conductor 25 together with a wire connector 30 to the top portion of LED chip 20. As such, heat generated by LED die 5 is dissipated through an electrical and heat conductor 25. This is not an optimum configuration to effectively dissipate heat to the ambient atmosphere. This sub-optimum configuration is due to the relatively long heat path provided by electrical and heat pathway, which causes a relatively high amount thermal resistance.
Light 35 is produced by LED die 20 within each LED package 5. A cavity 40 is provided within each of LED packages 5 and each cavity 40 contains a single LED die 20. This configuration allows combinations of side emitting LED packages 5 which together provide a relatively small range of colors. The range of colors is limited in that each LED die 20 emits a single color of light 35, and LED dice 20 are disposed relatively far apart from one another along light guide 10.
Thinner light guides and smaller product packages are necessary for thinner LCD displays. In order to provide a the largest possible aperture opening in a high quality LCD screen, product thickness and height should be reduced to dimensions as small possible with improved light coupling with the light guide. In order to provide good color mixing, red, green and blue LED dice should be placed close to each other while simultaneously providing an efficient heat path to ambient temperature.